Argasid or soft ticks are obligate ectoparasites of a wide variety of flying and land vertebrates. Most soft ticks reside in the dens, burrows, caves, and nests of their hosts and require multiple hosts to complete the prolonged, physiologically slow life cycle. Argasid ticks have existed since the late Paleozoic to early Mesozoic eras. The genera Ornithodorus and Argas were original genera and existed partially as we know them today. Other genera and species of soft ticks have become extinct. Prehistoric reptiles were probably the first natural host of the early soft ticks. In the early Tertiary period, primitive bird and mammal lines expanded into many specialized orders that replace reptiles as the dominant terrestrial hosts. Because of their smaller size and their varied physiologies, these "new" vertebrates filled many more ecological niches than the early reptiles did. The argasid ticks became adapted to microhabitats associated with nests, roosts, dens, caves, and lairs inhabited by birds or mammals. The large argasid ticks survived in association with porcupines, warthogs, wild pigs, and hyenas. The smaller argasid ticks evolved along with birds, rodents, bats and insectivores (Hoskins and Cupp, 1988).

In general, the argasids are likely to have several nymphal stages as part of their life cycle, and may have as many as 5 to 8 nymphal instars before they mature into adults. If the adult ticks are blood feeders, it is possible that they will take several blood meals after they reach sexual maturity. Two genera have been found to bother cats. Species of Ornithodoros have been observed to atack cats; this tick is parasitic in all life stages. Although some 100 species of Ornithodoros have been described, only two are known to attack cats. Only two species of Otobius have been described, but both have been recovered from cats. Adults of Otobius are not parasitic.


Hoskins JD, Cupp EW. 1988. Ticks of veterinary importance. Part II. The Argasidae family: Identification, behavior, and associated diseases. Comp Cont Ed Prac Vet 10:699-709.